Closing the immunization gap: Overcoming barriers for new vaccine introduction in Southeast and South Asia.

Many middle-income countries (MICs), particularly the ones ineligible for Gavi support, are falling behind in achieving Immunization Agenda 2030 targets. This study aims to compare the vaccine introduction status of national immunization programs across 13 Southeast and South Asian countries (Bangladesh, Cambodia, Lao PDR, Myanmar, India, Indonesia, Pakistan, Philippines, Viet Nam, Malaysia, Singapore, Sri Lanka, and Thailand) and identify key enablers and barriers associated with the new vaccine introduction. Through an extensive narrative review of public data as well as published papers and reports, we compared the new vaccine introduction and associated key factors across three country groups based on their Gavi funding status. Countries eligible for Gavi's MICs support approach showed slower progress in introducing pneumococcal conjugate vaccine, human papillomavirus vaccine, and rotavirus vaccine, with fewer vaccine-preventable diseases (11.25 vs. 12) and vaccines recommended by the World Health Organization (8.3 vs. 9.2) included in their national immunization programs compared to Gavi-eligible peers. Major barriers include underdeveloped decision-making processes, limited domestic financing, high vaccine prices, and gaps in immunization system readiness. To accelerate progress, countries must strengthen governance and financing mechanisms, optimize resource use for a better-performed program, and leverage targeted technical support from global partners. Closing these gaps is essential to expanding equitable access to life-saving vaccines and safeguarding regional health security.